Ординатура / Офтальмология / Английские материалы / Refractive Lens Surgery_Fine, Packer, Hoffman_2005

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Fig. 20.6.

The roughened 0.3-mm aspirator allows removal

of cortical material and polishing

of the capsule

through these microincisions. At the conclusion of bimanual phacoemulsification, perhaps the greatest disappointment is the need to place a relatively large 2.5-mm incision between the two microincisions in order to implant a foldable IOL. An analogy to the days when phacoemulsification was performed through 3.0-mm incisions that required widening to 6.0 mm for PMMA IOL implantation is clear. Similarly, we believe the advantages of bimanual phacoemulsification will prompt many surgeons to try this technique, with the hopes that the “holy grail” of microincision lenses will ultimately catch up with technique. Although these lenses are currently not available in the USA,companies are developing lens technologies that will be able to employ these tiny incisions.

Ultimately, it is the surgeons who will dictate how cataract technique will evolve. The hazards of and prolonged recovery from large-incision intraand extracapsular surgery eventually spurred the development of phacoemulsification. Surgeons who were comfortable with their extracapsular skills disparaged phacoemulsification, until the advantages were too powerful to ignore. Similar inertia has been evident in the transition to

M. Packer · I. H. Fine · R. S. Hoffman

Fig. 20.7.

This blunt, smooth dual-side port irrigator may

be used during irrigation/aspiration to safely manipulate cortical or epinuclear material in the capsular bag

foldable IOLs, clear corneal incisions, and topical anesthesia. Yet the use of these practices is increasing yearly. Whether bimanual phacoemulsification becomes the future procedure of choice or just a whim will eventually be decided by its potential advantages over traditional methods and by the collaboration of surgeons and industry to deliver safe and effective technology.

References

1.Girard LJ (1978) Ultrasonic fragmentation for cataract extraction and cataract complications. Adv Ophthalmol 37:127–135

2.Girard LJ (1984) Pars plana lensectomy by ultrasonic fragmentation, part II. Operative and postoperative complications, avoidance or management. Ophthalmic Surg 15:217–220

3.Shearing SP, Relyea RL, Loaiza A, Shearing RL (1985) Routine phacoemulsification through a one-millimeter non-sutured incision. Cataract 2:6–10

4.Crozafon P (1999) The use of minimal stress and the teflon-coated tip for bimanual high frequency pulsed phacoemulsification. Presented at the 14th meeting of the Japanese Society of Cataract and Refractive Surgery,Kyoto, Japan, July 1999

Chapter 20

5.Tsuneoka H, Shiba T, Takahashi Y (2001) Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refract Surg 27:934–940

6.Tsuneoka H,Shiba T,Takahashi Y (2002) Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results. J Cataract Refract Surg 28:81–86

7.Tsuneoka H, Hayama A, Takahama M (2003) Ultrasmall-incision bimanual phacoemulsification and AcrySof SA30AL implantation through a 2.2 mm incision. J Cataract Refract Surg 29:1070–1076

8.Agarwal A, Agarwal A, Agarwal S, Narang P, Narang S (2001) Phakonit: phacoemulsification through a 0.9 mm corneal incision. J Cataract Refract Surg 27:1548–1552

9.Pandey SK, Werner L, Agarwal A, Agarwal A, Lal V, Patel N, Hoyos JE, Callahan JS, Callahan JD (2002) Phakonit: cataract removal through a sub-1.0 mm incision and implantation of the ThinOptX rollable intraocular lens. J Cataract Refract Surg 28:1710–1713

10.Agarwal A, Agarwal S, Agarwal A (2003) Phakonit with an AcriTec IOL. J Cataract Refract Surg 29:854–855

11.Agarwal A,Agarwal S,Agarwal A, Lal V, Patel N (2002) Antichamber collapser. J Cataract Refract Surg 28:1085–1086; author reply 1086

12.Hoffman RS, Packer M, Fine IH (2003) Bimanual microphacoemulsification: the next phase? Ophthalmology Times 15:48–50

Microincisional cataract surgery (MICS) and operating through incisions of 1.5 mm or less are no longer new concepts in cataract surgery. Understanding this global concept implies that it is not only about achieving a smaller incision size, but also about making a global transformation of the surgical procedure towards minimal aggressiveness.

The incision size has been an important issue of investigation for many years, starting from reducing the size from 10 mm in intracapsular surgery to 7 mm in extracapsular cases, and finally from 3.4 mm to 2.8 mm using the phacoemulsification technique. The need to reduce the incision size was mainly for the purpose of reducing the induced

astigmatism, as modern cataract surgery is also refractive surgery. The other essential factor in the development of a new technique was how we could reduce the amount of energy being liberated inside the eye when using ultrasound emulsification. Until now the amount of energy being liberated or the power used to operate a cataract inside the eye has not been determined. As it is a source of mechanical, wave-shock, constitutional and thermal damage, this energy and power delivered inside the eye has an effect on the ocular structures. The thermal effects of this liberated energy affect all the intraocular structures, endothelial cells, corneal stroma, and incisions.

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The main issues and steps involved in the transition from phacoemulsification to MICS may be summarized as follows:

1.Fluidics optimization: MICS surgery should be performed in a closed environment. Because the probe fits the incision exactly, fluid outflow through the incision is minimal or absent. Taking into account the closed chamber concept, we need to optimize the probe function and diameter to balance the outflow and inflow that is taking place every second in this new environment [1].

2.Bimanuality and separation of functions:

The use of both hands simultaneously is another factor that added to the success of MICS surgery. The surgeon should be aware that working with two hands means working with irrigation and aspiration separately. In this way, irrigation and aspiration not only become part of the procedure, but also become instruments in the hands of the surgeon [1].

3.New microinstruments: The newly developed microinstruments have been designed to perform their function, while at the same time acting as probes. They do not necessarily need to be similar to the traditional choppers or forceps, which were mostly manufactured or created in the extracapsular era. These new specifically designed instruments, coordinated with the fluidics and combined with the new maneuvers, will improve efficiency compared with normal phacoemulsification that has been performed until now through “small” incisions [1].

4.Lasers: Lasers have become a technological possibility in performing cataract surgery. It is true that their capability of handling very hard nuclei is subject to debate. However, the elegance of laser, the very low levels of energy developed inside the eye, and the possibilities of improving the efficiency of this technology in the future makes them attractive for the MICS surgeon.

J.L. Alio · A. Galal · J.-L. R. Prats, et al.

5.Ultrasonic probes: Ultrasonic probes have to be modified in order to be used without sleeve. Taking off the sleeve is not the only way to use the probes in performing microsurgery [2, 3]. These probes should be designed to be used more efficiently, manipulating through microincisions without creating any tension in the elasticity of the corneal tissue. Furthermore, the friction created between the probe and the corneal tissue should be avoided with the special protection and smoothness of the external profile of the probe.

6.New intraocular lens (IOL) technology:

The technological development that enables operation of cataracts through a 1.5- mm incision should be adequately balanced with the development of IOL technologies capable of performing this surgery with IOL implantation though this microincision.At present, different IOLs of new designs, new biomaterials and new technologies are available for implantation through microincisions. Should we change the material, develop the optic technology, or both?

21.1MICS Surgical Instruments

Surgical instruments are important for safe and adequate MICS surgery. With a minor movement of the surgeon’s fingers, the metal instruments respond more than expected, uniting the fingers and the instruments to achieve excellent manipulation during MICS surgery (Fig. 21.1).

The instruments are finger-friendly and each has its own function. Once the surgeon becomes accustomed to them, they will be a new extension to his or her fingers inside the eye [1].

1.The MICS microblade is a diamond or stainless-steel blade that can create a trapezoidal incision from a 1.2- to 1.4-mm microblade (Katena Inc., Denville, NJ, USA) [1].

Chapter 21

Fig. 21.1. MICS surgical instruments

2.The MICS capsulorrhexis forceps (Katena Inc., Denville, NJ, USA) has microtriangular tips that can be used to puncture and grasp the capsule to perform the capsulorrhexis with a single instrument. It can also be used for other intraocular maneuvers such as grasping the iris to perform small iridotomies or to cut pre-existing synechia in the anterior or posterior chambers [1].

3.Alio MICS prechoppers are for bimanual use and, as opposed to the single-handed prechopping technique, can be used for all types of cataracts regardless of the hardness. The tip has a blunted square hook that should be introduced gently underneath the anterior capsular rim, with one instrument opposite the other [1].

4.The MICS hydrodissector or irrigating fingernail (Katena Inc., Denville, NJ, USA) facilitates manipulation of the nucleus fragments, as well as functions as an irrigating instrument. It can also be useful to

divide the nuclear fragments further. The forward-directed pointing tip, which has a highly blunt point-like end, is like a fingernail – hence its name. The irrigating fluid exits through a large port (1 mm) directed under the tip. This feature helps to push away the posterior capsule to obtain stable fluidic control in the anterior chamber when combined with the phacoemulsification or MICS aspirating tip. The flow rate or the free irrigation flow of this instrument is 72 cc/min, which is considered the highest flow of any instrument performing the same function in the market. This generates anterior chamber stability regardless of the high vacuum level in MICS [1].

5.The MICS irrigating chopper (Katena Inc., Denville, NJ, USA) was designed to chop medium to hard cataract if prechopping has not been performed. It has a sharp pointed triangular-shaped tip,which is angled downward to “chop” off segments of the nucleus. The irrigating fluid exits through a large port (1 mm) directed under the tip of the instrument [1].

6.The MICS aspiration handpiece (Katena Inc.,Denville,NJ,USA) has a bullet-shaped tip designed for easy entry through a paracentesis incision and a 0.3-mm diameter aspirating port close to the tip in the interior part of the curvature. This design works to maintain the fluid balance in the anterior chamber when used with the MICS irrigating fingernail and MICS chopper, and while aspirating the residual cortex [1].

7.The intraocular manipulator (Katena Inc., Denville, NJ, USA) is multifunctional and efficiently helps in iridolenticular synechia dissection,IOL manipulation and other intraocular maneuvers such as vitreous knuckles or stabilization of the IOL. The conical base is the same diameter as the internal MICS incision in order to maintain the stability of the anterior chamber, thus preventing viscoelastic outflow [1].

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8.MICS scissors (Katena Inc., Denville, NJ, USA) have a 23-gauge (0.6-mm) shaft, so they fit exactly through a very small paracentesis. They have extremely delicate blunt-tipped blades, which are ideal for cutting synechia and capsular fibrosis and membranes, as well as for performing small iridotomies [1].

21.2Low-Ultrasound MICS

21.2.1 Mackool Tips

Mackool tips generate less heat at the incision compared to non-Mackool tips. The thickness of the polymer sheathing the tip is only 50–75 microns, which is much less than that of the infusion sleeve; its thermal conductivity is also much less than that of conventional infusion sleeve material. This tubing system also prevents the spraying effect caused by the solution coming out of the irrigating tip, which occurs when power settings higher than 30% are used for MICS.

Most of the tips are three-quarters of an inch long and have a 45° angulation. Soft and moderately hard nuclei up to +2 hardness can be easily emulsified by using low-ultrasound MICS (LUS-MICS); prechopping will shorten the time of surgery and the energy delivered inside the eye. Hard nuclei of grade 3 or over are more amenable to LUS-MICS,which is capable of emulsifying hard nuclei of any density.

21.2.2 Incisions

After the surgical field has been isolated and an adjustable eye speculum (Duckworth & Kent,England) has been inserted,the positive corneal meridian is marked and two trapezoidal incisions of 1.2 mm internally and 1.4 mm externally are performed using the Alio corneal keratome. An external incision of 1.4 mm will be adequate for instrument

J. L. Alio · A. Galal · J.-L. R. Prats, et al.

manipulation. The two incisions are performed in clear cornea 90° apart, at 10 and 2 o’clock, followed by the injection of 1% pre- servative-free lidocaine diluted 1:1 in balanced salt solution.

21.2.3Prechopping (Counter Chopping Technique)

After the capsulorrhexis is performed using Alio’s capsulorrhexis forceps, the prechopping is performed. This is a bimanual technique, requiring the use of both hands with the same efficiency. This technique allows manual cut and division of the nucleus, without creating any grooves prior to the MICS procedure. In order to protect the endothelium and to perform an adequate counter chopping technique,more dispersive or cohesive viscoelastic material is injected. The technique of counter prechopping could be applied to all surgical grades of cataract density (up to grade +5).A chopper is introduced through one of the two incisions, depending on the surgeon’s preference.A nuclear manipulator is introduced through the other incision to decrease the stress on the capsule and zonules being inserted beneath the anterior capsulorrhexis edge. The rounded microball tip of the nuclear manipulator will protect the posterior capsule during the prechopping procedure. The tips of the nuclear manipulator and the chopper should be aligned on the same axis, together with the hardest point of the nucleus along the direction of the lens fibers; appropriate force is then applied between the two instruments. After cracking the nucleus into fragments, the nucleus is rotated and the maneuver is repeated on the other axis to crack the nucleus into four quadrants. Once the fragments have been obtained, the MICS Mackool tip and Alio hydromanipulator fingernail are introduced to manipulate and emulsify the fragments [1].

21.2.4Low-Ultrasound MICS Surgical Steps

The MICS technique can be performed using either phacoemulsification (LUS-MICS) or a laser (laser-MICS). After termination of prechopping, the Accurus or Infiniti machine is adjusted according to the settings described previously. The LUS-MICS tip and Alio’s hydromanipulator fingernail are introduced through the two incisions and an inferior segment is mobilized and brought in contact with the MICS tip, assisted with Alio’s hydromanipulator, in order to be emulsified. After the elimination of the first hemi-nucleus, the second prechopped hemi-nucleus is rotated to the distal portion of the bag and Alio’s hydromanipulator is used to mobilize the segments, making them easy to emulsify. Using this technique reduces the tendency for the nuclear material to come up into the anterior chamber during the procedure, and maintains its position within the epinuclear cover. Following the emulsification of all the nuclear segments, the epinuclear rim is trimmed in the different quadrants to remove all the cortical material remaining in the capsular bag. An adequate ophthalmic viscosurgical device is injected deep in the capsular bag to reform the bag and prepare it for IOL implantation; this helps to force the Viscoat anteriorly, facilitating its removal to prevent a postoperative rise in intraocular pressure [1].

21.3MICS versus Phacoemulsification: a Clinical Study

In a prospective, comparative, clinically controlled, masked study of a consecutive series of 100 eyes (50 patients), 50 eyes were operated with the MICS technology and 50 eyes were operated using conventional phacoemulsification. The patients had a mean age of 65.5 (45–86) years. Mean cataract grade was 3.01 with the lens opacities classification system III grading scale [4].

Patients ranging between 40 and 90 years:

1.Cataract eyes with a grade of 1–4

2.Normal clear corneas

3.Low or a minimal degree of astigmatism

4.Normal anterior segment

5.Normal retina and posterior segment

6.Normal intraocular pressure

Eyes with any ocular pathology were excluded.

21.3.2Preand Postoperative Examinations

All patients had a full ophthalmologic examination, preoperatively, at 1 week, 1 month and 3 months postoperatively:

1.Uncorrected and best corrected visual acuity

2.Anterior and posterior segment examination

3.Intraocular pressure measurement

4.Endothelial cell count using the SP 2000 P TOPCON machine

5.Laser flaremeter using the FC 1000KOWA laser flaremeter

6.Cataract density evaluation

21.3.3Operative Parameters

Only one memory and prechopping technique was used in both groups:

1.Phacoemulsification parameters:

(a)Aspiration: 550 cc/min

(b)Power: 20–30%

(c)Flow rate: 20 cc/min

2.MICS operative parameters:

(a)Aspiration: 550 cc/min

(b)Power: 20–30%

(c)Flow rate: 20 cc/min

The eyes included in the study were divided into the following two groups:

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1.Group I: MICS versus regular phacoemulsification (100 eyes) in the following parameters:

(a)Incision size

(b)Cataract grade

(c)Endothelial cell count

(d)Laser flare

(e)Pachymetry

(f)Mean emulsification time

(g)Mean power

(h)Mean effective phacoemulsification time

2.Group II: MICS versus regular phacoemulsification (40 eyes of 24 patients) in the following parameters:

(a)Postoperative astigmatism

(b)Intraoperative saline consumption

21.3.4Results of LUS-MICS

Microincision cataract surgery using ultrasound or laser offers the advantage of having a superior biological effect on the ocular structures compared with conventional pha-

J. L. Alio · A. Galal · J.-L. R. Prats, et al.

coemulsification procedures. A study of the parameters that control the procedure in both techniques found the following.

Working in a closed compartment while operating through the microincisions is characteristic of MICS surgery. The pressure of the anterior chamber was found to be higher in MICS surgery than in conventional phacoemulsification.

The vacuum used during surgery was found to be higher in MICS surgery, which is essential in performing this type of surgery.

The percentage of phacoemulsification differed according to the machine used. The grades of cataract operated with different machines were compared.A lower percentage of phacoemulsification was performed when using MICS 30and 300-burst modes (Accurus system),but using the 300-burst mode delivered less power to the ocular tissue when the power was calculated (Fig. 21.2).

Microincision cataract surgery offers the advantage of lowering the percentage of cells loss during the procedure. Comparing the re-

sults of endothelial cell count preand postoperatively, there was no statistically significant difference between the numbers, although the cell loss was reduced in MICS surgery. The flare and inflammatory cells developing after the procedure were also found to be equal and even lower after MICS surgery (Table 21.1).

21.3.4.1Group I

This group included 100 eyes of 50 patients divided in the following way:

1.Phacoemulsification: 50 eyes

2.MICS: 50 eyes

The means and standard deviations of the

cataract grade, incision size, endothelial cell

Table 21.3. Mean changes in pachymetry

count, flare and cells in the anterior chamber, phacoemulsification time, percentage power and effective phacoemulsification time are shown in Table 21.2.

21.3.4.2Group II

Twenty eyes (11 patients) operated with MICS were compared to 20 eyes (13 patients) operated with phacoemulsification. The eyes included in this group provided data about astigmatic changes and saline consumption, which were compared between the two techniques.

1.Astigmatic changes: using vector analysis to detect the postoperative changes in astigmatism:

(a)MICS group:

MICS can be performed using laser energy, which is as safe as ultrasound energy. The use of either source of energy permits:

1.Visual acuity improvement on the first postoperative day

2.Reduction of the inflammatory reaction postoperatively

3.Lower percent of in endothelial cell loss

Improving both techniques will open the way to emulsification of all grades of nucleus density; this could be achieved by improving the safety and the fluidity of the low-ultrasound

tween 1 and 0.5 D

(b) Phacoemulsification group:

(i)Four eyes had a change of ≤0.5 D

(ii)Six eyes had a change ranging between 0.5 and 1.0 D

(iii)Ten eyes had a change of more than 1 D

2.Saline consumption and pachymetry: the differences between the two groups are illustrated in Tables 21.3 and 21.4.

21.4Advantages of MICS

Performing small incisions in cataract surgery has a number of theoretical advantages:

1.Fast visual recovery and improved visual outcome

2.Decrease in postoperative astigmatism

3.Reduction in the anatomical healing time

4.Fewer complications

5.IOL insertion through microincisions is now possible

6.Reduction in the operating time

more vacuum that helps to maintain continuous contact between the crystalline lens to be removed and the laser aperture.

21.5Conclusions

Microincision cataract surgery today is becoming a popular technique in crystalline lens surgery. With the new developing technology of phacoemulsification machines and power settings, together with adequate instruments, all the cataract grades are amenable to MICS. Refractive lens exchange using the MICS technique has the advantage of preventing induced astigmatism and wound complications.